The present invention relates to a rapid coupling, particularly for refrigerant lines but not restricted to such use. The coupling has a socket and a nipple which can be inserted into it. It includes a locking device for the locking the coupled position between the socket and the nipple. That device has a bead protruding radially outward on the nipple. A cage mounted in the socket includes expandable holding fingers which grip behind the inserted bead.
A rapid coupling of this type is known, for instance, from U.S. Pat. No. 4,923,228. The socket of that rapid coupling has spring fingers which cooperate with a shoulder arranged on the nipple and which hold the two parts together in coupled position.
The disadvantage of such rapid couplings is, in particular, that the mechanic who assembles the two parts cannot see whether the two parts are completely coupled. An incomplete connection causes a leak during operation.
Known rapid couplings are particularly disadvantageous when they are used in places which are not visible to the mechanic. This frequently occurs in automobile construction, where the rapid couplings are concealed from the mechanic, for instance, by parts of the engine. It is difficult for the mechanic using the sense of feel (his hands) to determine whether the two coupling parts are properly assembled. There is also a great danger that, due to a defective connection, a leak will occur which might later lead to loss of refrigerant during operation.